The present invention relates to an improved apparatus and method for accurately sampling staple fibers. More particularly, the present invention relates to a static-air-pressurized automatic sampler having a smooth, convex fiber sample collection surface.
There are several generic manufacturing processes which may be employed in the production of staple synthetic fibers, including "melt spinning", "wet spinning", and "dry spinning." These three manufacturing processes differ from one another by the extrusion method they employ. As disclosed in the published literature, many specific variants of each of the three generic processes have been developed. However, all of these processes have in common the assembly of fiber bundles comprising many thousands of filaments, subsequently followed by cutting these into relatively short or staple fiber. Clumps of the cut staple fiber, of varying size and density, fall out of the cutting apparatus, either directly into the baler or into a transfer system which conveys them to a baler.
A typical process for the manufacture of polyester staple fibers may be briefly described as follows. Polyester resin, typically in chip form, is melted in an extruder and is pumped via a plurality of metering pumps through a filter packing and then through a multiple-hole spinnerette, which forms the molten polyester into a plurality of filament-like forms. The extruded filament-like forms are immediately cooled below the glass transition temperature of the polyester, thereby forming the actual filaments. A fiber finish composition is applied to the cooled polyester filaments. The filaments from all spinnerettes of the spinning machine are plied to form a spin cable, which is typically collected by deposition into a large can. The spin cables from a plurality of cans are subsequently fed from a creel to a stretch line. The assembly of spin cables on the stretch line (typically termed a "tow" or "tow band") is recoated with the fiber finish, and stretched to orient the filaments. In order to provide cohesion between the fibers necessary for subsequent textile processing, the fiber tow is crimped in a stuffer box, which produces a relatively wide band of crimped fiber called a crimper tow. The crimper tow is heat set, cut into staple fiber and baled. Alternatively, in order to produce fiber possessing a higher modulus, the fiber tow may be crimped after being heat-set, then cut into staple fiber and baled.
In the manufacture of staple fibers it is important to monitor and control various chemical and physical characteristics of the fibers, such as denier, tenacity, elongation at break, modulus, shrinkage in hot air or hot water, finish content, quantity of fused or undrawn fibers present, the length of the fibers, and their "openness" (the density and cohesiveness of the staple fiber mass). It is well known that these and other chemical and physical characteristics of staple fibers are strongly predictive of the performance of these fibers in the subsequent processes by which these fibers are converted into finished products and strongly influence the characteristics of the finished products. The chemical and physical characteristics of staple fibers must be controlled within limits appropriate to the intended application(s) if the fibers are to be suitable for the intended application(s). An accurate knowledge of the chemical and physical characteristics of staple fibers is necessary for proper control of the staple fiber manufacturing process, and for accurate grading of the product.
The many manufacturing circumstances which can lead to unintended and inappropriate chemical and physical staple fiber characteristics may be classified into two groups: "continuous circumstances" which operate continuously to consistently produce unintended characteristics, and "intermittent circumstances" which operate intermittently to produce isolated "pockets" of fibers with unintended characteristics. Testing of any staple fiber sample taken will normally reveal defects which are being produced continuously in the manufacturing process. However, other defects occurring only intermittently are not likely to be reliably detected unless the sample tested is statistically representative of the staple fiber product increment represented.
Manual sampling of staple fibers as they fall from the yarn cutting apparatus to a baler is still a commercial practice. Normal procedure has been to open a sampling port and manually grab a handful of falling staple fiber, which is then analyzed for length and "openness". The sampling frequency is typically one grab per fiber bale (normally either 500 or 750 pounds). This method is both expensive and ineffective in providing statistically representative samples.
Staple fibers have also been manually sampled after they have been baled. Typically, the baler operator hand-pulls three samples from the face of the bale--one handful of fiber in the middle, one handful from the upper right hand corner and one handful from the lower left hand corner. This method is also expensive and statistically unrepresentative. The manual pulling of staple fiber from the baled fiber mass often breaks individual fibers, thereby leading to inaccurate fiber length analysis. Furthermore, accurate analysis of the "openness" of the fibers is impossible once they have been compressed into a bale.
Prior artisans have proposed automatic sampling of staple fibers. For example, M. Wilder et al, "Automatic Sampler for Flowing Staple Fiber," U.S. Pat. No. 3,841,159 (Oct. 15, 1974) discloses a sealed yarn sample container connected to a yarn transfer line by a conduit. The container has supported internally a yarn catching means such as a hook which may be thrust through the conduit into the transfer line where it catches a small wad of flowing staple. Then the yarn catching means is returned to the sample container where the fiber sample drops off by gravity into the container. The entire sample container is sealed to withstand the pressure of the transfer line, thereby precluding the removal of sample for analysis while the sampler is operating.
J. Woodley, Jr., "Fiber Sampling Apparatus," U.S. Pat. No. 3,315,530 (Apr. 25, 1967) discloses an automatic fiber sampler located between the yarn cutting apparatus and a fiber packaging system. The fiber sampler comprises a housing adjacent the fiber stream to be sampled, a hollow probe reciprocably mounted in the housing, the hollow probe having one end open and the other terminating in a probe tip of specific design. In operation partial vacuum is applied to the probe tip by aspiration, thereby attracting and holding a sample of fiber from the fiber stream. The probe is then withdrawn from the fiber stream. When the probe is fully retracted pressurized air is sent through the hollow probe, thereby blowing the retained staple fiber sample off the probe tip and through a transfer chute into a sample collection box.
The use of suction, like mechanical grabbing, to collect a sample of staple fiber is undesirable since such sampling may alter some of the physical properties of the sampled fibers, thereby providing a statistically unrepresentative staple fiber sample.
Automatic sampling apparatus for other applications have also been proposed, particularly for granular or powdery material. For example, J. Abonnenc, "Automatic Volumetric Device for Taking Samples of Granular or Powdered Material," U.S. Pat. No. 4,024,765 (May 24, 1977) discloses a horizontal, cylindrical sampling probe having a trapezoidal sample recess for the removal of a fixed volume of material from the sampling zone. The sampling probe is reciprocably inserted into and withdrawn from the sampling zone by pneumatic or hydraulic rams. The sampling probe is rotated about its major axis to discharge the sampled material into a sample hopper. The sampler is sealed to prevent contamination by the sampling area. Similarly, R. Starks, "Sampling Apparatus," U.S. Pat. No. 3,595,087 (July 27, 1971) discloses a hollow, rotable, and reciprocal sampling tube for use with granular materials of differing sizes and configurations
Other samplers have been proposed for specific applications, typically involving pressurized lines and apparatus or materials under vacuum. For example, D. Sweeney et al, "Sampling Device for Rotary Cone Vacuum Dryer," U.S. Pat. No. 3,554,038 (Jan. 13, 1971) discloses the use of a helical rotating wire to continuously remove sample from an evacuated rotating dryer without having to stop the dryer or release the vacuum. A. Thompson, "Line Sampling Device," U.S. Pat. No 3,659,461 (May 2, 1972) uses a sealed sampler employing a sampling plunger and poppet valves to sample products flowing in a pressurized line such as partially digested wood chips. N. Risdal, "Sampler for Flowing Pressurized Dry Material," U.S. Pat. No. 4,433,587 (Feb. 28, 1984) discloses, inter alia, an inclined sample tube which is alternately projected upwardly into and withdrawn downwardly from the stream of flowing material. The tube has a sample receiving slot in its upstream side and a discharge port in its bottom side. Employing a series of seals and an obstruction in the sample receiving slot, the apparatus can sample from a pressurized line while maintaining its outlet ports at atmospheric pressure.
Research and development resulting in the present invention was initiated only after a commercial automatic sampler was purchased and demonstrated to be unacceptable. Problems associated with the commercial sampler included an unacceptably slow sampling rate, failure to properly release sampled fibers into the sample fiber chute, and contamination of the sampler by staple fibers when the sampler was not operating.
The present invention remedies these problems and in so doing satisfies a long felt but unsatisfied need in the synthetic fiber manufacturing industry for an automatic fiber sampler which can rapidly and repetitively sample staple fibers falling within a fiber chute at a sampling frequency of up to 50 samples per bale.